97-99% Purity Alumina (ASTM D2442 Type III, IEC 60672 Type C-795)
Type III alumina is a grade of alumina. It has the second lowest strength compared to the other variants of alumina. The graph bars on the material properties cards below compare type III alumina to other oxide-based engineering ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
Mechanical Properties
Compressive (Crushing) Strength
2240 MPa 330 x 103 psi
Elastic (Young's, Tensile) Modulus
310 GPa 46 x 106 psi
Flexural Strength
340 MPa 49 x 103 psi
Fracture Toughness
4.2 MPa-m1/2 3.8 x 103 psi-in1/2
Knoop Hardness
1290
Poisson's Ratio
0.22
Shear Modulus
120 GPa 18 x 106 psi
Tensile Strength: Ultimate (UTS)
230 MPa 34 x 103 psi
Electrical Properties
Dielectric Constant (Relative Permittivity) At 1 Hz
9.0
Dielectric Constant (Relative Permittivity) At 1 MHz
8.8
Dielectric Strength (Breakdown Potential)
12 kV/mm 0.47 V/mil
Electrical Dissipation At 1 Hz
0.00067
Electrical Dissipation At 1 MHz
0.00067
Electrical Resistivity Order of Magnitude
14 10x Ω-m
Other Material Properties
Density
3.8 g/cm3 240 lb/ft3
Maximum Temperature: Mechanical
1650 °C 3000 °F
Maximum Thermal Shock
210 °C 420 °F
Melting Onset (Solidus)
2040 °C 3700 °F
Specific Heat Capacity
890 J/kg-K 0.21 BTU/lb-°F
Thermal Conductivity
24 W/m-K 14 BTU/h-ft-°F
Thermal Expansion
7.2 µm/m-K
Common Calculations
Stiffness to Weight: Axial
46 points
Stiffness to Weight: Bending
60 points
Strength to Weight: Axial
17 points
Strength to Weight: Bending
22 points
Thermal Diffusivity
7.2 mm2/s
Thermal Shock Resistance
7.4 points
Followup Questions
Further Reading
ASTM D2442: Standard Specification for Alumina Ceramics for Electrical and Electronic Applications
Ceramic and Glass Materials: Structure, Properties and Processing, James F. Shackelford and Robert H. Doremus (editors), 2008
Ceramics and Composites: Processing Methods, Narottam P. Bansal and Aldo R. Boccaccini (editors), 2012
IEC 60672-3: Ceramic and glass-insulating materials - Part 3: Specifications for individual materials
Springer Handbook of Condensed Matter and Materials Data, W. Martienssen and H. Warlimont (editors), 2005